Tag Archives: Layer 3 Switch

Over the years, the average network has been dominated by the Layer 2 switch. Now as network complexity increases and applications demand greater functions from the network, Layer 3 switches are coming out of the data center and high level enterprise settings. Why this happens? Layer 2 vs Layer 3 switch: What’s the difference? Which one should I deploy?

Layer 2 vs Layer 3 Switch
The main function of a Layer 2 is to help the traffic from devices within a LAN reach each other. A Layer 2 switch does this by keeping a table of all the MAC addresses it has learned and what physical port they can be found on. The MAC address is something that operates within Layer 2 of the OSI model (what defines how networks operate). Traffic being switched by MAC address is isolated within the LAN those devices are using. Therefore, when you need traffic to cross between LANs (or VLANs) is when we need a Layer 3 network switch.

The most common Layer 3 device used in a network is the router. A router is able to look into the Layer 3 portion of traffic passing through it (the source and destination IP addresses) to decide how it should pass that traffic along. Since a router holds information about multiple networks (LAN WAN VLAN) it is also able to pass traffic along between these networks. This is routing. The Layer 3 switch functionally exists somewhere between being a Layer 2 switch and being a Gateway Router. It can be best described by what more it does compared to a Layer 2 switch and what less it does compared to a Gateway Router.

Layer 2 vs Layer 3: What Makes Layer 3 Switch Different?
When comparing the Layer 2 switch to a Layer 3 switch the first thing to look at is what additional software functionality you are getting. When a switch supports Dynamic Routing Protocols, it’s no longer a strictly Layer 2 switch. Because static routing allows traffic to be routed between VLANs. In fact, the switches that add only Static Routing to their software features are considered to be somewhere between a Layer 2 and full Layer 3 switch. Sometimes called Layer 2+ or Layer 3 Lite. Unlike Layer 2+ switch, Layer 3 switch is Dynamic Routing ,which are used to link large networks together and share routing tables between them. They can also allow for dynamic routing of multicast traffic on the network.

Layer 2 vs Layer 3: To Choose a Layer 2 Switch or Layer 3 Switch?
Now that we know the difference between the two layers, what metrics would you choose one over the other comes down to the flexibility of being able to route the packets. If you need to send data within a LAN, use Layer 2 switch. If you need to send the data to other buildings on campus or to a client site, use Layer 3 switch. FS.COM provides a series of Layer2/3 10G/40G/100G switches to meet Data Center and Enterprise Ethernet network requirements. If you are interested, welcome to visit our website www.fs.com or contact us via sales@fs.com for more detailed information.